We discuss the effects of collisional enhancement of Balmer lines on the determination of the primordial helium abundance. To this aim, we present a photoionization model of the metal-poor extragalactic H 0 region SBS 0335-052. We show that the derived helium abundance (Y) of this H 0 region depends on the amount of collisional excitation affecting

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We have used William Herschel Telescope/INGRID Ks images on two high-latitude fields, the Coppi and Groth strips, to obtain galaxy number counts over ~180 arcmin2, to a depth of Ks~21.0. Detection efficiency corrections as a function of object size have been calculated on each pointing. We have used a signal-to-noise threshold in two complementary

We use a high-resolution collisionless simulation of a Virgo-like cluster in a ΛCDM cosmology to determine the velocity and clustering properties of the diffuse stellar component in the intracluster region at the present epoch. The simulated cluster builds up hierarchically and tidal interactions between member galaxies and the cluster potential

In Tingley (cite{tingley}), all available transit detection algorithms were compared in a simple, rigorous test. However, the implementation of the Box-fitting Least Squares (BLS) approach of Kovács et al. (cite{kovacs}) used in that paper was not ideal for those purposes. This letter revisits the comparison, using a version of the BLS better

This volume documents the contributions presented at the 5th Scientific Meeting of the Spanish Astronomical Society (SEA). Covering a wide range of topics, the 154 contributed papers give a comprehensive overview of the current state of Spanish astronomy. The Proceedings include special reviews by Dr. V. Trimble and other experts dealing with the